The present invention relates, in general, to hand brakes for railway freight cars and, more particularly, this invention relates to an improved hand brake lever interface that is suitable for use with a single-cylinder, truck-mounted brake rigging.
There is presently known in the prior art a single-cylinder, truck-mounted brake rigging, as shown in U.S. Pat. Nos. 4,613,016 and 4,793,446, which has been designed for use with truss-type brake beams. In this respect, the braking force applied through the rigging acts on the respective brake beams at the beam midpoint where maximum resistance to bending forces is effective by reason of the beam strut arm transferring the load between the beam compression and tension members. Such a single-cylinder rigging, when combined with truss-type brake beams, is believed to offer maximum efficiency of operation at a relatively low cost.
In U.S. Pat. No. 5,069,312 there is taught a hand brake for a single cylinder truck mounted railway car brake. This patent is assigned to the assignee of the present invention and the teachings therein are is incorporated herein by reference thereto.
Disclosed therein is a hand brake system for use with a truck mounted single cylinder brake rigging which includes a truss type brake beam. There is a single hand brake pivotal lever supported intermediates its ends by a twisted transfer link that is, in turn, fixed to the brake rigging transfer lever. A fulcrum end of the hand brake lever is free to engage the bearing surface of thrust block mounted on the brake beam at the juncture of the brake beam tension and struck members in order to allow the point of engagement between the fulcrum end and the bearing surface to change with rotation of the hand brake lever. In addition, the fulcrum end of the hand brake lever is arranged with two, spaced apart arcuate segments that successively engage the bearing surface of the thrust block during rotation of the hand brake lever to change its lever ratio and, accordingly, limit the degree of rotation of the hand brake lever.
The present invention provides an improved hand brake lever interface for a single cylinder truck-mounted railway car brake for use with a hand brake system for a railway vehicle including first and second spaced-apart brake beams. First and second transfer levers are pivotally connected at a point intermediate the ends thereof to a respective one of the first and second brake beams. First and second force-transmitting members are interconnected between corresponding arms of the first and second transfer levers. Such first force-transmitting member including a brake actuator device operable in response to the supply of fluid pressure thereto for increasing the length of the first force-transmitting member, to accordingly increase the spaced-apart distance between the first and second brake beams. A transfer link is connected to the first transfer lever so as to be arcuately movable therewith in a plane parallel to the plane of rotation of the first transfer lever. The improvement comprises a thrust block disposed on the first brake beam. The thrust block having a pin member disposed therein. There is an actuating lever having a pivotal connection at a location intermediate the ends thereof with the transfer link closely adjacent one end of the actuating lever there is an arcuate portion rotateably engageable with the pin member and being adapted to receive a hand brake force.
It is, therefore, one of the primary objects of the present invention to provide an improved hand brake lever interface for a single cylinder truck-mounted railway car brake having a pin and lever geometry that will keep the lever properly positioned in the vertical direction which will help reduce the drag force due to misalignment of the cylinder transfer lever and the hand brake transfer link.
Another object of the present invention is to provide an improved hand brake lever interface for a single cylinder truck-mounted railway car brake which is capable of interacting with a brake rigging of the foregoing type so that the hand brake force and the pneumatic power brake force may be applied at the midpoint of the respective brake beams, without requiring any additional levers to transmit the hand brake force from one brake beam to the other.
Another object of the present invention is to provide an improved hand brake lever interface for a single cylinder truck-mounted railway car brake which is capable of applying the desired hand brake force through the pneumatic brake rigging components without imparting any significant torque force on the brake beam and/or rigging components.
A still further object of the invention is to provide an improved hand brake lever interface for a single cylinder truck-mounted railway car brake configured so as to cause the hand brake lever ratio to change during operation in order to limit its range of travel and thereby prevent interference with the truck axle.
It is an additional object of the present invention to provide an improved hand brake lever interface for a single cylinder truck-mounted railway car brake which can be retrofitted onto existing systems.